The present invention relates to water treatment systems, and more particularly to a bulb intensity control circuit for an ultraviolet household water treatment system.
Household water treatment systems are gaining popularity, particularly in areas with less than ideal potable water. A household unit is mounted on a single tap to treat selectively water flowing through the tap. Treatment may include filtration, sterilization, or both.
The most effective water treatment systems include ultraviolet (UV) irradiation for sterilizing the water stream. It is well known that such UV treatment kills bacteria and viruses with an extremely high degree of reliability. The water to be treated is routed through a container, and a UV light source within or adjacent to the container directs UV light through the water stream.
Two considerations factor into the intensity of the UV light. First, it is desirable to operate the light at optimum intensity to achieve the maximum "kill rate" whether water is flowing or stagnated. Second, it is desirable to avoid excessive UV light intensity to avoid excessive warming of water "stagnated" within the treatment chamber when water flow stops. Stagnation occurs whenever the tap is not used for a considerable period of time, for example, overnight. Prior artisans have accommodated these considerations by selecting a single optimum intensity of a constantly on bulb to balance "kill rate" and temperature rise. The UV bulb is always at optimum intensity, and the first water out of the tap is properly treated. When water flow ceases, the optimum UV intensity prevents bacteria from recolonizing in the treatment chamber. However, the temperature rise of the stagnated water is undesirable.